1. Field of the Invention
The present invention generally relates to coating pans and to panning apparatus used to produce coatings or shells on a mass of centers. In particular, the present invention relates to a split-pan for a panning apparatus and to a panning apparatus incorporating a split-pan that provide for the simultaneous coating of different masses of centers with different coatings in a single apparatus, such that the different center/coating combinations are not intermingled or mixed.
2. Related Background Art
Panning and film coating are related industrial processes for preparing coated centers. Typically, the term “panning” is used with regard to the application of sugar-based coatings, such as, e.g., sucrose and dextrose to masses of centers. The term “film coating” is used with regard to application coatings that are not based on sugar to masses of centers. However, the basic processes used in panning and film coating are substantially the same. Each process comprises the repetitive application of thin layers of a coating solution or composition onto an intermixed mass of centers, while mixing the mass of centers, and the drying of each layer of coating solution or composition. Each process is performed in a rotating drum or “pan”. Panning often comprises three distinct repeating steps; namely, application of the coating solution, distribution of the coating solution on the centers, and drying the coating solution. In contrast, the film coating process often comprises the simultaneous application, distribution, and drying of the coating solution. However, in each process, thin layers of coating material are built up on the center with each application to form the desired shell or coating. The application, distribution, and drying steps may be performed simultaneously or sequentially.
Panning and film coating are used to apply coatings to a variety of different types of centers, including, but not limited to, pellets, tablets, pills and molded or granulated products. Examples of coated centers include pharmaceuticals in the form of pills, tablets, and the contents of time-release capsules; chemical products, such as detergents; and foodstuffs, such as candy. Coatings are typically used to prevent degradation and decomposition of the centers from exposure to air and humidity, to give the coated object a decorative appearance, and have been known to prevent the melting of certain chocolate candies in consumer hands.
Panning and film coating apparatus and processes performed by them for coating centers are well known in the art. A typical panning or film coating apparatus comprises a coating pan and mechanisms for introducing a coating solution and a drying gas into the pan. A mass of centers is introduced into the coating vessel. The mass of centers is then intermixed, a layer of the coating solution is applied to the centers, and the coating layer is dried with the drying gas. The coating may be dispersed by spraying or pouring the coating solution onto the mass of centers. Applying the coating solution while intermixing the mass of centers prevents the coated centers from adhering to each other, and helps insure uniformity. The drying gas, which is often dry air, may be introduced simultaneously with or subsequent to the application of the coating solution.
For example, U.S. Pat. No. 2,652,805 to D'Angelo discloses an apparatus for coating tablets, pills, and other small objects. The disclosed coating apparatus comprises a rotating drum, a drive motor, and optionally, one or more blowers. Pills or tablets placed in the drum are tumbled or intermixed by the rotation of the drum. A coating material, added to the drum, is distributed onto the surface of the pills or tablets. Multiple coats of one or more coating materials may be applied with the apparatus.
U.S. Pat. No. 3,357,398 to Gross discloses a method and apparatus for coating tablets. The apparatus comprises a tiltable perforated drum or pan mounted on a shaft within a housing, a drive motor, and a mechanism for forcing a drying medium, i.e., air, through an inlet in the housing, through the perforated pan, and out an outlet. Tablets are loaded in the perforated drum, which is then rotated to mix them. An atomized coating material is sprayed onto the tablets and the drying medium is passed through the inlet and the perforated drum, as the tablets are mixed.
U.S. Pat. No. 4,245,580 to Okawara discloses a device for coating granular solids. The apparatus comprises a double-cone rotary drum, which is perforated to permit the flow of gas through the drum, a drying gas supply, a drying gas exhaust, annular insulating covers for the drum, and mechanisms for tilting and changing the height of the drum to facilitate loading and unloading. Coating material is sprayed on granular material in the drum, and the drying gas is passed through the drum, as the drum rotates.
U.S. Pat. No. 5,495,418 to Latini et al. discloses an automatic panning system that comprises a rotatable drum in which a mass of centers is tumbled and coated with a solution to form a shell, a spray arm for applying a coating solution, an air flow system to provide a drying air flow, and control means. The coating process consists of the repetition of separate spraying, distribution, and drying cycles in which the condition of the air, the drum speed, and the cycle timer are monitored and controlled by the control means.
However, every known prior art film coating and panning apparatus, such as those described briefly above, allows coatings to be applied to just one mass of centers at a time. Because of the nature of such apparatus, and the process that they perform, a coating material introduced into the coating pan or drum is applied to substantially all of the centers in the mass. Therefore, during production, a different panning apparatus is required for each combination of coating and center that is prepared at any given time. To increase the number of center/coating combinations that can be simultaneously processed using prior art pans requires additional panning apparatus, which, in turn, requires additional capital costs and space. Therefore, a need exists for a panning apparatus that can process two or more center/coating combinations simultaneously. The present invention provides such an apparatus.